Magnesium base alloy



Patented July 26, 1938 UNITED STATES PATENT OFFICE 2,124,562 MAGNESIUM BASE ALLOY John A. Gann, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich, a corporation oi. Michigan No Drawing. Original application August 2, 1937,

Serial No. 156,943. Divided and this application February 5, 1938, Serial No. 188,930

4 Claims. (01. 75-168) The present invention relates to magnesium Cast alloys alloys and more particularly to those in which magnesium is the predominant constituent. Nominalcomposmon Most of the present commercial uses for mag- (Mg=remaindcr) Tm Yield Pewt nesium alloys are due to their high strength and W 1b a g high strength-weight ratio. 11 these characterd Mn b Sn A1 istics could be further improved, the field of applicati'on of these light weight alloys would be 1 2 2 300 4 m 8 a greatly extended. 3 Q3 v I The principal object of this invention is to 3 a: 1 2 2:: 2: 2': produce magnesium alloys having improved phys- 2 8 2 ical properties. A more specific object is to pro- 2 8 2 mm mm duce magnesium alloys that are amenable to heat g 3-2 g g'aag g'ggg treatment. Other objects and advantages will appear as the description proceeds.

This invention is based on the discovery that Sam! the properties of the magnesium-cadmium-manganese-lead alloys as described in United States 3 g: g g Patent No. 1,850,613 may be improved to a very marked extent by the addition of relatively small 6 M 2 6 1mm amounts of aluminum without appreciably in- 6 M 2 6 4 "3 a I: creasing the gravity or the alloy. I have likewise 3 Q3 1 2 discovered that maximum property improvement 3 l 2 3mm mo is obtained when these alloys are subjected to the 1 well known methods of solution heat treatment m and solution heat treagnent plus aging. Equally o 2 6 16 8m important is the improvemeht in foundry char- 6 n m m acteristics, specifically melting and casting, as 6 M 2 6 occasioned by the presence of aluminum. I have I g 33 g 3% 3;; found that the advantages occurring from the 3 0. 1 2 10 29,000

addition of aluminum are present when approximately 1 to 12 per cent of aluminum are added to magnesium alloys containing from about 0.5 to 10 per cent of cadmium, from about 0.1 to 0.5 per cent of manganese, from about 0.5 to 10 per cent of lead, and from about 0.5 to 8 per cent of tin.

Specific examples of the property improvements that result in producing my new alloy by the addition of aluminum to the known magnesiumcadmium-lead-tin alloy are shown in the following tables where illustrations are given of cast, solution heat treated, and solution heat treated and aged alloys.

I have likewise discovered that the strength characteristics or this new magnesium-cadmiummanganese-lead-tin aluminum alloy may be still further improved by the addition of zinc in amounts ranging from about 0.5to 8 per cent. In the cast alloys this improvement is most pronounced in the case of yield strength where the addition of 2 to 6 per cent of zinc gave increases amounting to 20 to per cent. In the solution heat treated alloys the presence oi zinc gave increases in both tensile strength and yield, strength amounting to. as much as 25 to per cent. The most pronounced sheet 0! inc, however, was in the solution heat treated and aged alloys where improvements in yield strength were as high as 80 per cent. Specific examples of the beneficial eifect of zinc are given in the accompanying table.

Nominal composition (Mg-remainder) Condition 2;? Value Cd Mn Pb Sn A] Zn 0 0. 2 6 4 Omt Y. 8. 10,900 0 0.5 2 6 4 m--- 12,700 3 0.3 l 2 6 .do (in 12,800 3 0.3 1 2 6 6 .do do 15,500 2 0.5. 8 2 4 S.H.T.' T. BL- 31,700 2 0.5 8 2 4 .do .-do 33,900 3 0.3 1 2 6 do Y. 8... 12,100 3 0.3 1 2 6 4 .do (in 15, 2 0.5 8 2 4 S P. H. T. T. B 30,8) 2 0. 5 8 2 4 -.do .do 34,400 3 0.3 1 2 0 ..do Y. S... 12500 3 0. 3 1 2 6 do 7 22. 700 2 0.5 8 2 4 ....do ..do... 10,700 2 0.5 8 2 4 4 .do do 17,700

gmgield strsngthhlbifi. ini.l1 ensilesrengt .sq. i S. H. T.=Bolntion heat treated. 4 8. P. H. T.=Bolution heat treated and aged.

The establishment of the percentage of each metal in these new alloys depends on the use for which the material is intended. In general, I prefer to use alloys containing more than 80 per cent of magnesium and less than 20 percent of total added metals, but where the material is to be used for the production of wrought shapes, the alloy is usually restricted to compositions containing more than 90 per cent of magnesium and less than 10 per cent of total added metals. For the production of castings, the alloy should preferably contain approximately 85 to 92 per cent of magnesium, 4 to 10 per cent of aluminum, 1 to 5 per cent of cadmium, 0.1 to 0.3 per cent of manganese,

1 to 8 per cent of lead, and 1 to 6 per cent of tin.

ent in amounts ranging from about 2 to 4 per cent. For the production of wrought shapes by extrusion and forging, the alloys should, in general, contain these metals in the following proportions: 1 to 8 per cent of aluminum, 0.5 to 3 per cent of cadmium, 0.1 to 0.5 per cent of manganese, 0.5 to 2 per cent of lead, 0.5 to 3 per cent of tin, and 0.5 to 2 per cent of zinc. If the alloy is to be fabricated by rolling rather than by extrusion or forging, the percentage of aluminum should preferably lie within the range of 1 to 5 per cent.

My new polynary alloys may be prepared by the methods usually employed for melting and alloying metals with magnesium, such as adding the respective alloying metals singly or jointly to a bath of molten magnesium protected from oxidation by a cover of fluid flux. The solution heat treatment for the zinc-free alloys may consist in heating the material for 20 hours at,430 C. followed by air cooling, or, when zinc is present in the alloy, 12 hours at 320 C. plus 16 hours at 420 0. followed by air cooling. The aging treatment consists of approximately 16 hours heating at 175 C., subsequent to the above solution heat treatment. Plastic deformation operations, such as extruding, forging, and rolling are best conducted at temperatures between 300 and 400 C.

This application is a division of my co-pending application Serial No. 156,943, filed August 2, 1937.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the ingredients and the steps herein disclosed, provided those stated by any of the following claims or their equivalent be employed.

I particularly point out and distinctly claim as my invention z- 1. A magnesium-base alloy containing from approximately 1 to 12 per cent of aluminum, from about 0.5' to 10 per cent of cadmium, and from about 0.1 to 0.5 per cent of manganese, and from about 1 to 10 per cent of lead, and from about 1 to 8 per cent of tin, and from about 0.5 to 8 per cent of zinc, the balance being magnesium.

2. A magnesium-base alloy consisting of approximately 4 to 10 per cent of aluminum, and from about 1 to 5 per cent of cadmium, and from about 0.1 to 0.3 per cent of manganese, and from about 1 to 8 per cent of lead, and from about 1 to 6 per cent of tin, and from about 2 to 4 per cent of zinc, the balance being magnesium.

3. A magnesium-base alloy consisting of approximately 1 to 8 per cent of aluminum, and about 0.5 to 3 per cent of cadmium, and from about 0.1 to 0.5 per cent of maganese, and from about 0.5 to 2 per cent of lead, and from about 0.5 to 3 per cent of tin, and from about 0.5 to 2 per cent of zinc, the balance being magnesium.

4. A magnesium-base alloy consisting of approximately 4 per cent of aluminum, and 6 per cent of cadmium, and 0.5 per cent of manganese, and 2 per cent of lead, and 6 per cent of tin, and 2 per cent of zinc, the balance being magnesium.

.JOHN A. GANN. 

